Adams County, Illinois

Adams County
Location within the U.S. state of Illinois
Illinois's location within the U.S.
Coordinates: 39°59′N 91°11′W / 39.99°N 91.19°W / 39.99; -91.19
Country United States
State Illinois
Founded1825
Named afterJohn Quincy Adams
SeatQuincy
Largest cityQuincy
Area
  Total
871 sq mi (2,260 km2)
  Land855 sq mi (2,210 km2)
  Water16 sq mi (40 km2)  1.9%
Population
 (2020)
  Total
65,737
  Estimate 
(2023)
64,441
  Density75/sq mi (29/km2)
Time zoneUTC−6 (Central)
  Summer (DST)UTC−5 (CDT)
Congressional district15th
Websitewww.co.adams.il.us

Adams County is the westernmost county in the U.S. state of Illinois. As of the 2020 United States census, the population was 65,737. Its county seat is Quincy. Adams County is part of the Quincy, IL–MO Micropolitan Statistical Area.